The long-term goals of this project are to investigate, using in vitro techniques, the role of trophic interactions in the survival and differentiation of visual neurons, as well as the mechanisms regulating selective neuritic growth in the visual system. Specifically, we intend to carry out the study of: 1) the maturation of chick embryo neural retinal and optic lobe neurons and nonneuronal cells in purified monolayer cultures, using cytochemical techniques and, in particular, those related with neurotransmitters; 2) trophic interactions between neural retina and optic lobe neurons in monolayer co-cultures; 3) effects of glial cells on survival and maturation of retina and optic lobe neurons; 4) developmental changes in specific requirements for neuritic production by neurons; and, 5) physical models for the analysis of nerve fiber growth, guidance and regeneration.